Extendible boom



United States Patent Inventors Frank C. Rushing;

Albert B. Simon, Ellicott City, Maryland 684,241

Nov. 20, 1967 Dec. 1, 1970 Westinghouse Electric Corporation Pittsburgh, Pennsylvania in corporation of Pennsylvania Appl. No. Filed Patented Assignee EXTENDIBLE BOOM 1 Claim, 2 Drawing Figs.

US. Cl. 138/156, 52/108; 343/877 Int. Cl. 013 1/12 Field olSearch 113/8,12;

138/1S6,162,16917l;156/218;220/75, 76; l61/(lnquired); 52/108; 182/41; 343/877 [56] References Cited UNITED STATES PATENTS 167,796 9/1875 Somers 138/170X 207,606 9/1878 Ketcham 138/169 219,645 9/1879 Miller 220/76 556,819 3/1896 Hartman 138/156 828,899 8/1906 Parker 220/76 Primary Examiner-Laverne D. Geiger Assistant Examiner- Edward J Earls Attorneys-F. H. Henson, E. P. Klipfel and D. F. Straitiff ABSTRACT: An improved extendible boom of the unrolled thin wall strip, self-forming, hollow tube-type having overlapping tabs both inside and outside at its longitudinally extending seam; the improvement wherein the tabs of each seam edge consist of an alternating series of wide and narrow tabs with tapered side edges, with the wide tabs of one seam edge overlapping narrow tabs and abutting the tapered side edges of wide tabs, of the other seam edge.

Patented Dec; 1, 1970 3,543,806

FI G.I

INVENTOR WITNESSESI F k C R a ran u s mg Albert B.Simon FIG.2

sxrsunmu: BOOM BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION In accord with the present invention, the employment of wide tabs with tapered side edges which overlap narrower tabs and abut at their tapered side edges corresponding edges of adjacent wide tabs, eliminates clearance between tabs along the seam and prevents backlash during subjection of the boom to a torsional moment, as in employment of the boom for rotary positioning of a sensor or device at its end.

BRIEF DESCRIPTION OF THE DRAWING In the drawing: FIGS. 1 and 2 are fragmentary views of the extendible boom showing details of the improved locking tab construction in .unengaged and engaged positions. respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, the extendible boom I of the present invention, as heretofore, is formed of a narrow, elongated strip II of thin springlike material, such as heat treated metal a few thousandths of an inch thick, which is rolled onto a reel (not shown) and held in its rolled up state for storage. When released lengthwise from the reel under proper control and guidance it curls together edgewise and forms itself continuously into a hollow tubular shape as a rod or boom.

In accord with the present invention, opposing series of wide and narrow tabs and 16, respectively, are formed alternately in continuation along the longitudinal edges 12 of the strip 11; the narrow tabs I6 of one edge being opposite to the wide tabs 15 of the other edge. The two side edges 17 ofat least each of the wide tabs 15 are tapered or slanted equal degrees in diverging directions progressively inward of such edges, and so alined at opposite edges of the strip across the seam that such edges 17 of the wide tabs 15 on one seam side abut the tapered-side edges 17 of the adjacent wide tabs 15 of the opposite seam side when the seam is formed by causing such wide tabs 15 to overlapthe narrower tabs 16, as in FIG. 2, or vice versa. This arrangement prevents longitudinal clearance between the wide tabs 15 due to the slope of the abutting tapered or slanted side edges 17, while the overlap of tabs, narrow and wide, both inside and outside the boom I0 provides resistance to folding collapse of the seam both inwardly as well as outwardly. A taper having a considerable component at right angles to the direction of seam extension in the region of contact assures locking action against longitudinal movement during twisting of the boom, while any longitudinal component of such taper forwardly facilitates the introduction of such tabs on opposite seam sides to one another when the seam springs together during erection of the boom. A taper of 10 from being perpendicular to the longitudinal axis of the boom is suitable, for example, for the tapered side edges 17 in their region of contact.

We claim: I. An improvement in an extendible boom comprising: an elongated relatively thin springlike strip having a series of tabs formed on each of its opposite longitudinal edges for assuming overlapping positions to form an abutting seam therebetween when the strip is free to curl together edgewise into a cylindrical configuration; the improvement thereof wherein; the series of tabs on each strip edge consists of alternate wide and narrow tabs, the wide tabs of one edge being alined with the narrow tabs ofthe other edge for mutually overlapping relationship therebetween to form the seam; and

the wide tabs each have inwardly diverging side edges so located that each side edge of the wide tabs of one seam side contacts a point on the tapered edge of the adjacent wide tabs of the other seam side coexistent with the aforesaid mutually overlapping relationship with the narrow tabs. I 

